The present invention relates to a method for forming conductor members such as electrodes by plating, to a manufacturing method of a semiconductor element using the conductor members forming method and to a manufacturing method of a thin-film magnetic head.
In general, conductor members such as electrodes formed on a substrate should have a thickness larger than a thickness of elements formed on the substrate because required are the conductor members to be exposed at a position higher than the elements.
In order to fabricate such thick conductor members by plating, generally, a photoresist material for thick-film is first coated by a low-speed spin coating method, the coated photoresist is patterned by exposure and development, and thereafter plating is executed to form the conductor member pattern.
However, since such photoresist material for thick-film has a high viscosity, it is difficult to completely fill unevenness formed on a conductive film with the photoresist material, namely the photoresist material has a low wettability, causing air bubbles to remain in the unevenness portion. Such air bubbles may deform the resist pattern resulting a poor shape in plated conductor members to be provided.
Japanese patent publication No.10124826A discloses a method for preventing such air bubbles from producing by coating first a low viscosity resist material on a conductive film and then by coating a high viscosity resist material on the coated low viscosity resist material.
According to this conventional method, however, it is necessary to use a plurality kinds of resist material with different viscosities and also to coat them under different coating conditions causing the coating process to complicate.
It is therefore an object of the present invention to provide a method for forming conductor members, a manufacturing method of a semiconductor element and a manufacturing method of a thin-film magnetic head, whereby conductor members can be formed in a good and desired shape only by adding a very simple process.
According to the present invention, a method for forming conductor members includes a step of coating an organic solvent on a conductive film to form an organic solvent layer, a step of coating a resist material on the organic solvent layer to form a resist layer, a step of patterning the resist layer to form a patterned resist layer, and a step of plating a conductive material using the patterned resist layer to form the conductor members.
Also, according to the present invention, a method for forming conductor members includes a step of coating an organic solvent on a conductive film to form an organic solvent layer, coating a resist material on the organic solvent layer to form a first resist layer, coating a resist material on the first resist layer to form a second resist layer, patterning the first and second resist layers to form a patterned resist layers, and plating a conductive material using the patterned resist layers to form the conductor members. Furthermore, according to the present invention, a manufacturing method of a semiconductor element or a thin-film magnetic head includes a step of forming electrodes using the above-mentioned conductor members forming method.
Just after forming the organic solvent layer on the conductive film, a resist material is coated. Thus, the interface part with the organic solvent layer of the resist layer melts partially, and the melted portion serves as a low viscosity resist which enters into the unevenness of the conductive film so as to fill its level difference. Therefore, no air will remain in the unevenness to prevent air bubbles from generation and as a result no deformation of the resist layer will occur. In addition, this advantage can be obtained only by adding a very simple process for coating the organic solvent resulting that the manufacturing process will not become complicated.
It is preferred that an edge portion of the first resist layer is removed by an edge rinse method before the second resist layer is formed, and that an edge portion of the second resist layer is removed by the edge rinse method before the plating. In this case, it is more preferred that a width of the removed edge portion of the first resist layer is larger than a width of the removed edge portion of the second resist layer.
In general, if a photoresist material for thick-film is spin-coated, the resist material returns in the direction of the center from the edge of the wafer due to surface tension, and therefore a projection of the resist layer is formed on the perimeter or edge portion of the wafer. This projection will prevent to bring the conductive film of the wafer intimate contact with the plating electrode. Thus, electrical conduction between the plating electrode and the conductive film becomes unstable and therefore stable plating cannot be expected.
Although it is possible to simultaneously remove the projections of the first and second resist layers on the wafer by the edge rinse method, if the width of the projections is wide, the removed area will become large and therefore the region for forming the elements on the wafer will becomes small causing a utilization efficiencies of the wafer to reduce.
However, if the second resist layer is formed after the edge portion of the formed first resist layer is removed by the edge rinse, the projection of the second resist layer is formed on the wafer where no first resist layer is remained due to the edge rinse. Thus, the height of the projection of the resist layer becomes very low. Furthermore, if the edge rinse of the second resist layer is performed such that the width of the removed area is smaller than the width of the removed area of the first resist layer, an extremely low projection height can be expected without increasing the whole width of the removed area of the resist layers. As a result, stable electrical conduction between the plating electrode and the conductive film can be obtained and thus plating of conductive material can be attained at a stable plating rate without narrowing the region for forming the elements.
It is preferred that the organic solvent is composed of a solvent component of the resist material. Since the solvent component of the resist material has a relatively low volatile and a relatively high viscosity, using of this as for the organic solvent is very desirable. Also, this solvent component of the resist material has a sufficient affinity for the resist material.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.